Breaking the digital-physical barrier in organic electronics materials discovery: application to finding anti-Kasha molecules.

Molecules which display two optical emission bands are very rare as they violate Kasha's rule, which states that fluorescence is normally observed only from the lowest energy excited state of a specific spin multiplicity (e.g. S1) due to efficient internal conversion from higher states after excitation. Here, we develop a combined virtual and experimental screening workflow to find new anti-Kasha emitters among those with a large energy gap between S1 and S2; a condition that favours optical emission from the higher excited state because of a reduced internal conversion rate. 140 000 chemically diverse and commercially available molecules are filtered through a computational funnel based on their computed S1-S2 gap, transition intensities and structural rigidity before being ranked by cost and purity from up-to-date information from the chemical supply chain. The absorption and fluorescence spectra have been measured for 15 potential candidates that have not been previously explored for this property. Seven of them display anti-Kasha emission, five displaying single emission from S2 and two displaying emission from multiple excited states (a particular case of dual emission). The lower energy emission of one of the dual emitters, however, originates from an aggregate state. The approach exemplifies the great potential of virtual screening approaches that take into account chemical availability and lead to an immediate validation of the predictions.